With a very early Shift of two, and a base card that can cost as low as one, you can get this powerful card on the field easily
The rest of the deck is primarily legendary creatures with useful utility like Eowyn, Fearless Knight for removal and evasion, Inga and Esika for ramp and draw, Ratadrabik of Urborg for removal insurance, and Shanid, Sleepers' Scourge for draw and evasion
Frenzied Saddlebrute can be swapped in for Thermo-Alchemist, since it requires you to cast multiple instants and sorceries on your turn to truly maximize its ability, something this deck doesn't really do
Even attacking with a cheap token triggers Raid
I remember the moment I decided to myself that Cats was the way to go
As for the Sphinx, Arjun, the Shifting Flame has about 33 nonland cards in the deck that you can squint at and go sure, that fits before cutting it down to 21 for good measure